DMR Glossary: TG, TS, Color Code, ESSID and Other Terms

If you have only just started getting acquainted with DMR digital radio, you have probably been buried in abbreviations: TG, TS, CC, BER, ESSID, AMBE... It all turns into mush. This article is a short glossary of the most essential terms in plain words and with examples. You don't have to memorize everything: come back here whenever you run into an unfamiliar acronym. And if you want to calmly get to grips with the technology itself from the very beginning, take a look at our article DMR from scratch.

Core concepts

DMR (Digital Mobile Radio)

This is an open digital radio standard adopted by the ETSI institute. Unlike an ordinary analog radio, here the voice is transmitted not as a "wave" but as a digital stream — encoded zeros and ones. Thanks to this, the link is cleaner, reaches farther for the same signal, and lets you carry text, coordinates and service data along with the audio.

TDMA (Time-Division Multiple Access)

A technology that lets two conversations run on a single frequency "in turns" by slicing the air into tiny time fragments. DMR uses TDMA with two streams, so a single frequency effectively works as two independent channels. You don't notice it — the switching happens dozens of times per second.

Timeslot (TS1 / TS2)

A timeslot (TS) is exactly one of the two time channels within a frequency. They are labeled TS1 and TS2. For example, on a repeater one conversation can run in TS1 while a completely different one runs simultaneously in TS2, and they don't interfere with each other.

Simplex and duplex

Simplex — receive and transmit happen on the same frequency, so you can only talk in turns (radio directly to radio). Duplex — receive and transmit are split across different frequencies, which a repeater needs in order to listen to you and relay the signal onward at the same time. A simple single-frequency hotspot works in simplex; a repeater works in duplex.

Network and routing

Talkgroup (TG)

A talkgroup is a virtual "room" where users gather by interest or geography: for example a regional group, a themed one, or a worldwide one. You select the desired TG on your radio — and you only hear those who are currently in that same room. For more on how groups attach to a channel permanently or temporarily, read the article Talkgroups: static and dynamic.

Reflector

A reflector is another way to bring people together into a shared conversation: you "connect" your hotspot or repeater to a reflector, and everything that arrives there is distributed to everyone connected. Historically reflectors came from the world of D-STAR and YSF, and in modern DMR networks their role has largely been taken over by talkgroups. How a reflector differs from a TG in practice is covered in the article Reflector and TG: what's the difference.

Repeater

A repeater is a fixed station that receives your weak signal and immediately retransmits it onward at high power from a good antenna. Thanks to this, a small handheld radio can "reach" tens of kilometers. A repeater works in duplex and is usually connected to the network over the internet.

BrandMeister

BrandMeister is the world's largest amateur DMR network, uniting thousands of repeaters and hotspots all over the world. It is the network most beginners connect to in order to get on the air on popular talkgroups. It is not hardware but a server infrastructure that you hook into through your hotspot.

Homebrew / HBP (Homebrew Protocol)

The Homebrew Protocol (HBP, sometimes HBlink) is the protocol by which hotspots and repeaters talk to network servers such as BrandMeister over the internet. When you see the words "Homebrew" or "MMDVM" in your hotspot's settings, this is exactly the connection method being referred to. For the user it is the "pipe" through which your voice goes out into the big network.

Hotspot and modem

Hotspot

A hotspot is a small personal access point that receives the signal from your radio and, through your home internet, connects it to the DMR network. In essence it is a tiny personal repeater on your desk that lets you work on the air even where there are no real repeaters nearby. A hotspot usually consists of a single-board computer (for example a Raspberry Pi) and a radio modem.

MMDVM (Multi-Mode Digital Voice Modem)

The MMDVM is that very radio board-modem inside the hotspot that "translates" the radio signal into digital data and back. The word "Multi-Mode" means it can handle not only DMR but also other digital modes (D-STAR, YSF, P25). When people say "MMDVM firmware," they mean the software of this board.

Color Code (CC)

The Color Code is a number from 0 to 15, a kind of "digital password" for the channel. For the radio and the repeater (or hotspot) to hear each other, their Color Codes must match, otherwise the signal is simply ignored. It is the equivalent of the CTCSS subtone from analog radios; for a detailed breakdown see the article Color Code: the digital subtone.

BER (Bit Error Rate)

BER shows what percentage of transmitted bits "arrived with an error" — it is the main indicator of digital signal quality. The lower the BER (ideally around 0%), the cleaner the link; values above 2–3% already mean crackling and dropouts. BER is convenient for tuning and calibrating a hotspot.

Voice coding and the air

AMBE vocoder (AMBE+2)

A vocoder is an algorithm that compresses the human voice into a very narrow digital stream. DMR uses the proprietary AMBE+2 vocoder from DVSI: it is exactly what turns your speech into compact data and reconstructs it at the other end. Why it is closed-source and how that affects equipment is covered in the article The AMBE vocoder.

Codeplug

A codeplug is a file with the full configuration of your radio: the list of channels, frequencies, talkgroups, Color Codes, contacts and zones. It is prepared in the CPS program on a computer and loaded into the radio. Experienced hams exchange ready-made codeplugs for a specific region so a beginner doesn't have to set everything up by hand.

RX Group List

The RX Group List is the set of talkgroups that the radio will "listen to" on a specific channel. If a group is not added to this list, you simply won't hear a conversation going on in it, even if it is on the air. That is why, when configuring a codeplug, it is important to gather all the groups you are interested in into the RX Group List.

Parrot / echo test

Parrot is a special talkgroup that records your transmission and immediately plays it back to you. It is the simplest way to check that your radio and hotspot are set up correctly and to hear how you sound on the air. If the "parrot" repeats your phrase, your link to the network is working.

Last Heard

Last Heard is a feed on network websites and in control panels showing who last got on the air and when: callsign, DMR ID, talkgroup and time. It is a handy way to check whether your call made it into the network and to see activity on the groups you care about.

Identifiers

DMR ID

A DMR ID is your unique digital number in the network, the equivalent of a phone number for a digital radio. It is tied to your callsign and is issued free of charge after your license is verified. Without a DMR ID you can't work properly in the network; how to get one is described in the article DMR ID: how to get one.

ESSID (Extended SSID)

An ESSID is two extra digits appended to your DMR ID to distinguish several devices under one number. For example, ID 2501234 with the suffixes 01 and 02 gives "2501234 01" for the home hotspot and "2501234 02" for the radio, and the network doesn't mix them up. This is handy when you have several hotspots at once — details are in the article Multiple hotspots and ESSID.